I'm an avid fleece user, and in my opinion, there are the Regulator fleeces (i.e. Polartec Thermal Pro), and there is everything else. The Regulator fleeces are just head and shoulders above the standard double-faced pile Polartec fleeces out there. They are lighter, warmer, more compressible, more durable, quicker drying, and more breathable. In short, they are, IMO, superior in every technical respect.
Because of this, I couldn't ever imagine choosing the Snap-T fleece over one of the Regulator fleeces. So my vote would obviously be a Regulator fleece.
As for which one, well, what kind of temperatures are you planning to use this fleece in? You mentioned that you were planning on using this fleece while hiking, biking, etc... If that's the case, then I think the R4 might be too warm for your intended use unless you are using it in very cold conditions. That R4 is a very warm fleece, and it's not as breathable as the R3 or the R2 because it has that windproof membrane.
IMHO, windproof fleeces are a waste of money, because they are sort of a one trick pony (outerwear in very cold weather). They aren't nearly as breathable as non-windproof fleeces and they weigh more too. I use my lightweight windshell (which will be with me anyways while backpacking and hiking) to protect my fleece from the wind, and when it's not windy, I have a fleece that is comfortable in a wider range of conditions.
Anyway, my vote for you would be the R2 fleece jacket (hugely versatile) or the R3 fleece jacket for a little more warm.
In case you're interested, here is a breakdown of the lowest comfortable temperature for me while wearing the current R2 jacket:
R2 + baselayer - 55 degrees fahrenheit (without wind and at rest) or 40 degrees fahrenheit (without wind, actively moving)
R2 + baselayer + 5oz windshell - 40 degrees fahrenheit (at rest) or 25 degrees fahrenheit (actively moving)
The R3 would probably push all the temps down by 5-10 degrees or so for me.
I hope this helps!